Off-course, if majority of your time is spent compiling gigantic C++ codebases, more power to you for using VIM. CPU load in code compilation hasn't been the bottleneck I ever faced and I think this applies to most folks. Plus CLion doesn't just arbitrarily start consuming CPU, if it is not doing indexing(and VIM simply can't do the kind of indexing that CLion does), it doesn't consume much CPU. In the idle state, it consumes very little CPU.

Then again, some seconds of CPU might be a good tradeoff against productivity in some scenarios.